Introduction to Cell – Structure and Type

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Understanding the intricacies of cell structure and types is paramount for students gearing up for government exams due to its broad applicability in various fields such as biology, medicine, and agriculture, all of which are often tested in these exams. A solid grasp of cellular organization, organelle functions, and cell types not only forms the basis of biological concepts but also aids in comprehending complex topics like genetics, immunology, and environmental science, which are frequently featured in government exam syllabi.

Contents hide
1 Introduction to Cell – Structure and Type
1.1 Cytology
1.2 Cell Theory –
1.2.1 Exceptions to cell theory
1.2.2 Cell Size:-
1.2.3 Cell Shape: –
1.3 Difference Between Prokaryotic and Eukaryotic Cells
1.4 Difference between Plant Cell and Animal Cell

Introduction to Cell – Structure and Type

Cytology

In this branch, the structure and function of cells are studied.  The word cell was given by Hertwig.
Cells were discovered by Robert Hooke; he saw dead cells in corks. Therefore, Robert Hooke is called the father of cytology.

  1. A. V. Leeuwenhoek was the first to look at living cells.
    During evolution, the first cells were formed by an abiotic process or chemical synthesis.

 

Cell Theory –

  1. Cell Theory presented by Maltheus Schelden and Theodore Schwann. According to this, the cell is the functional, structural and hereditary unit of life.
  2. Rudolf Virchow has said that new cells are formed from already existing cells.
  3. The cell principle is –
    (a) All living organisms are made up of cells and the product of cells.
    (B) All cells arise from pre-existing cells.

 

Exceptions to cell theory

 B and T lymphocytes – typical genetic material is absent.

 Multi Nucleate Organism: – Syncytium in animals, coenocyte in plants, slime moulds in Plimodium.

 Prions: – Only nucleic acids made by proteins are absent.

RBC: – Nucleus absent (nucleus is present in the RBC of camel and llamom)
Virus: – Acellular,   composed only of nucleic acids and  proteins.
Viriods:- There is only RNA particles.
Virions:- are passive carriers of the viral genome.

 Cell Size:-

Mycoplasma:- Smallest cell, 0.3 micrometer in length
Bacteria: – 3-5 micrometers
in length Human RBCs: – 7 micrometers
Nerve Cell: – Longest cell, 90cm in length

Boemeria nivea: – Longest plant cell

Acetabularia: – Longest unicellular plant
ostrich egg- largest single cell

Cell Shape: –

The cells are disc-like, polygonal, columnar, cuboid, threads similar or irregular.

Type of cell: –

  1. B. Van Neil classified cells into two classes:
  2. Prokaryotic cell:
  3. The cells of bacteria, blue green algae, mycoplasma (cell wall absent), PPLO (organisms like Pleuro pneumoniae) etc. are prokaryotic cells.
  4. The nucleus is less developed called nucleiod, it lacks histone proteins.
  5. Membrane ligaments lack cells.
  6. THE OUTERMOST OF THE CELLS IS GLYCOCALYX MADE OF POLYSACCHARIDES IN THE FORM OF HARD CAPSULES AND SOFT COATINGS (SLIME LAYER SLIME LAYER).
  7. Cell walls are made up of peptidoglycan.
  8. PLASMA MEMBRANES ARE MADE UP OF FATS, PROTEINS AND OLIGOSACCHARIDES.
  9. Bacteria are of gram + ve and gram –ve
  10. THE MESOSOME IS FORMED BY THE INGESTION OF THE PLASMA MEMBRANE. On which there are enzymes for respiration.
  11. IN ADDITION TO GENOMIC DNA, SINGLE CIRCULAR DNA IS CALLED PLASMID.
  12. Bacterial cells are motile or amotile.
  13. FLAGELLUM – CONSISTS OF THREE PARTS – FILAMENT, HOOK, AND BASAL BODY
  14. PILI AND FIMBRIAE – DO NOT PLAY A ROLE IN MOBILITY. But it helps to stick.
  15. RIBOSOMES 15-20nm, divided into 2 sub-units 50s and 30s -70s together –
  16. Ribosomes aid in protein synthesis.
  17. RNA+Ribosomes –>POLYRIBOSOMES POLYSOMES
  18. INCLUSION BODIES: PHOSPHATE GRANULES, CYANOPHYCIN, GLYCOGEN GRANULES, GAS VACUOLES.
  19. Eukaryotic Cell
  20. EU-developed, Karyon-
  21. They contain developed nucleus.
  22. They contain one or more nucleus.
  23. Their genetic material is arranged in chromosomes.
  24. It consists of membrane ligament cells.
  25. All plants, animals, fungi, protists contain eukaryotic cells.
  26. There is also a difference between plant and animal cells.

 

Difference Between Prokaryotic and Eukaryotic Cells

 

S.No. symptom Prokaryotic cell Eukaryotic cell
1. Example Bacteria , Cyanobacteria , Mycoplasma Algae , fungi, all plant and animal cells
2. Cell Size Micro 0.1-5 um diameter Large 5-20um Diameter |
3. Cell wall manufactured. Made from mucopeptides (peptidoglycones) From wall cellulose in plant cells
4. Satanga

(i)E.R.

          not present  

Well-developed, Work – Transport
(ii) Mitochondria

 

 

 not present

 

 

 Present in large numbers ;Work – Respiration
(iii) Plaque not present Plants only
 

 

 

 

 

 

 

  

 

 

 

 

 

 

 Functions present in cells – light

Synthesis,  collection of starchy protein fats
(iv) Goljikaya not present Well developed , work – exertive , accumulation of substances
(v) Lysosomes and paraoxisomes not present Present, function – digestion and dissolution
(vi) Microtubules not present Present, Function – Cell Skeleton Construction
(vii) Ribosomes Present, 70 types, function protein synthesis Present 80s of type, function protein synthesis
5. nucleus

(i) Centrifugal art

 

 

  

not present

 

 

  

Present Dual Art

 
(ii) Centralized

 

 

 

 not present

 

 

 

 Synthesis of present, working tRNA

In centrifugal membrane

 
(iii) Genetic material

 

 Scattered in the cytoplasm

 

 Bound

 

 
(iv) Histone protein

 

 not present

 

 

 present

 

 
(v) Multiplication Always haploid Haploid and diploid
6. Stellar not present Present in all animal cells
7. Misdeeds Paramicrobe, made up of a fibril in the bacteria present Subtle, whenever present 2+9  Structured
8. Cell division Misotic and meiosis divisions are not  there, chromatic divisions are non-formulaic divisions. Movement of chromosomes unknown | Rational fibers are not formed. There are mitotic and meiosis divisions . Clear movement of chromosomes |Rational fibers are formed.
9. Sexual reproduction True Sexual Reproduction Absent Sexual reproduction occurs
10. Protoplasm Thin The membrane is thick
11. breathing Often by non-aerobic respiration, by plasma membrane Aeration occurs, site mitochondria

 

Difference between Plant Cell and Animal Cell

 

S.No. Plant Cell Animal Cell
1. The cell wall is present. The cell wall is absent.
2.  Vacuole usually causes the nucleus to be at the periphery. Nucleus is present near the centre in the cell.
3. In higher plant cells, the stellate (centosome) is usually absent.

The exception is low-grade motile cells.

 Generally, the stellar body is present which helps in the formation of spindle fibir.
4. Plastids are present. Fungi are an exception to this. Plastids are absent .
5. Mitochondria are spherical or elliptical in shape. Mitochondria are tubular .
6. A long nuclear vacuole is present. There are many rituals which are peak in size .
7. During cell division, cytoplasm is normally divided by the cell plate method. The cytoplasm divides by groove and cleavage method.
8. Plant cells are capable of producing all amino acids, coenzymes and vitamins. Animal cells cannot produce all amino acids , coenzymes and vitamins .
9. Contractile vacuoles are not found in them. Contractile vacuoles can be found in them.  Which pumps out excess water.
10. The spindle formation after cell division is of the anastral type. The spindle formation during cell division is of the amphiastral type.
11. Lysosomes are present in small numbers. Lysosomes are present in greater numbers .
12. Spherosome is present. There is a lack of spherosomes.
13. The stored food is in the form of starch. The stored food is in the form of glycogen and fat.
14. Plasmodesmata are found . Plasmodesmata are lacking.

 

 

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